In modern computed tomography (CT) scanner systems of the third generation type, an X-ray source and detector array rotate about a subject or object to be scanned. During a scan, the source and detectors image the object at incremental scan angles. A process referred to as reconstruction generates a series of two-dimensional images or slices of the object from the captured data.
The source, detectors, and related components are mounted to a rotatable gantry supported by a rigid stationary frame. As the gantry rotates, a conveyor passing transversely through a central aperture in the gantry translates the object relative to the sensors. The X-ray source generates an electromagnetic energy beam which is attenuated by the object as the beam propagates to the detector array. Each time a beam is fired at the object, X-ray reflections scatter throughout the system housing.
In these systems, environmental safety is of utmost concern as exposure to X-ray energy is known to be harmful to humans. In current CT scanner embodiments, the entire scanner housing is lined with lead for absorbing X-ray energy to prevent emission into the environment external to the housing.
FIG. 1 is a cutaway side view of an X-ray shield configuration in accordance with the prior art. An X-ray source 20 and detectors 24 are mounted on a rotatable gantry 21. The X-ray source 20 generates a beam 26 which is directed toward detectors 24. A conveyor 32 introduces an object 36 into the path of the beam 26 which attenuates the beam and further causes the beam 26 to scatter throughout the conveyor tunnel area 46 and throughout the system within housing 22. A lead lining 34 is provided throughout the inner surface of the housing, and lead curtains 30 are provided in tunnel 46, to prevent scattered X-rays 28 from radiating into the environment external to the housing 22, protecting a human operator 44 from prolonged exposure to X-rays of otherwise released energy 38. The lead lining 34 must be sufficiently thick, for example 2.5 mm, to absorb and/or attenuate scattered beams 28, and therefore can add thousands of pounds to the system weight. Furthermore application of the lining 34 is tedious, resulting in high installation costs.